Terminal 30 Info

[tHatOne guY]

I'm looking for some info on terminal 30... B6 A4 1.8T is the vehicle in question, no codes, no issues as scanned by registered Ross-Tech.

First, where is terminal 30 located? Starter post? Under the driver side dash?
I have searched here and google and come across a few different answers but still unclear.

Second, what voltage should I see at terminal 30?

I checked the terminal 30 measuring blocks in VCDS with the engine running and only saw 11.98V so I measured the voltage at the battery with my DMM while the engine was running and saw 13.8V... I assume terminal 30 should be receive full source voltage i.e engine off full B+ voltage, engine running alternator output of 13.5-14.2V

Currently do not have service manual for the B6 chassis, looking to purchase though if someone is ready to sell. Thanks for looking guys.

[KHARDa4]

Yes you are correct anything referring to terminal 30 is battery voltage. Terminal 15 is ignition power when the key is turned. So 30 is hot all the time 15 only in the acc run position.

[tHatOne guY]

Any idea where can I find terminal 30?

[KHARDa4]

If you're looking at a diagram and it's referring to terminal 30. That is telling you source voltage is the battery. You should see 12v at anything showing terminal 30.

[diagnosticator]

The "30" circuit is +Bat 12 vdc as already advise. On the wiring diagrams, it is a horizontal line at the top of the wiring diagram. "30" is the constant unswitched power supply for a lot of different components.

[tHatOne guY]

Ok, so there is no single physical location for terminal 30 on the car?

I am concerned with this because I see almost 14vdc at the battery but only 11.9vdc at terminal 30 measuring blocks, engine running of course.

Just ordered a Bentley for this model on ebay, damn 90$ for the cd service manual.

[diagnosticator]

Ok, so there is no single physical location for terminal 30 on the car?

I am concerned with this because I see almost 14vdc at the battery but only 11.9vdc at terminal 30 measuring blocks, engine running of course.

Just ordered a Bentley for this model on ebay, damn 90$ for the cd service manual.

The "30" circuit powers anything and everything requiring +Batt constant Vdc power supply from the Battery. The "30" circuit voltage displayed by diagnostics measuring blocks, is the "30" circuit voltage seen by the ECU at the ECU. Due to circuit resistance and current flow in Amps load on the electrical system, the voltage at the ECU will be reduced compared to the +Batt and alternator output voltage. However, 11.9 vdc or 2.1 less voltage at the ECU shows that there is a higher than normal resistance occuring in a connetion to the battery positive in the circuit. Check for loose or contaminated connections between the battery and the wiring harness power supply "30" connection under the drive's side dash panel at the threaded terminal block, with three 5mm threaded studs and 8mm wrench size nuts. Low voltage can also be caused by loose or corroded ground connections from the battery to chassis ground, and any system ground connections to chassis ground. Loose or corroded ground connections result in higher than normal resistance through the circuit connections to chassis ground, also causing the voltage drop in the circuit/s.

[tHatOne guY]

Thanks.

I'll start under the dash driver side and voltage drop test my way back to the alternator and battery, repairing any bad connections I find. Appreciate the advice.

May be a good time to do a big 3 upgrade. My positive side battery cable has been very hot lately, I'm guessing the factory crimp is failing causing high resistance.

[diagnosticator]

Hot cables are evidence of excessive resistance in the cable connectors, or the cable is too small for the current load on the cable. Audi does not under size cables, but they could be larger specification however that would add weight and cost to the car with all the drawbacks offsetting the benefits.

[diagnosticator]

Hot cables are evidence of excessive resistance in the cable connectors, or the cable is too small for the current load on the cable. Audi does not under size cables, but they could be larger specification however that would add weight and cost to the car with all the drawbacks offsetting the benefits.